IOM 1210-1 • MAGNITUDE
®
MODEL WMC CHILLERS
34 www.DaikinApplied.com
o
peraTIon
BAS Alternate
In control strategies (I) through (V), the chiller MicroTech
®
II
is directly controlling the cooling tower fan staging, variable
frequency drives, and bypass valves. As an alternative, a BAS
can control these components based on a signal from the
MicroTech
®
II controller. See
Figure 42
.
Figure 42: BAS Alternate
Setting Tower Control Using the OITS Panel
MicroTech
®
II may assist in the head control either directly
or through inputs to a BAS to optimize performance and
efficiency. Using the MicroTech
®
II, up to four Digital Outputs of
Tower Staging along with three Analog Outputs (0-10 VDC) are
available. The three Analog Outputs are as follows:
1. Bypass Valve signal
2. Tower Fan VFD signal
3.
Tower Reset signal: Defined by a voltage to offset the
tower control setting. If the MicroTech
®
II is controlling
the tower, this signal is not used.
Setup for any tower control will be accomplished on the OITS
using the TOWER Setpoint Screen (see
Figure 31 on page
31
) and the VALVE Setpoint Screen (see
Figure 30 on page
30
).
Setpoint 1 (Cooling Tower Control) on the TOWER Setpoint
Screen sets the type of control. NONE is selected as default.
Choose TEMP for entering condenser water control or LIFT to
define the lift pressure between the Evaporator Pressure and
the Condenser Pressure.
Setpoint 3 (Cooling Tower Stages) on the TOWER Setpoint
Screen sets the number of tower stages that the tower has.
Setpoint 2 (Tower Bypass Valve / Fan VFD) on the TOWER
Setpoint Screen defines if and how the first two MicroTech
®
II Analog Outputs (Bypass Valve signal and Tower Fan VFD
signal) will be used with the Staging selected for the tower. A
BAS or other control may monitor these outputs to understand
when or how much the MicroTech
®
II would recommend for
proper head control on the WMC unit. The third Analog Output
(Tower Reset) is only configurable from the MicroTech
®
II
controller. Commissioning setup of this 0-10 VDC signal, that
will represent the MicroTech
®
II recommending increased
head pressure by a reset voltage, is typically done by the
Daikin Applied startup technician. Setup instructions for each of
the five tower control strategies are provided next.
(I) NONE: Tower Fan Staging Only (This is the default
setting but it is NOT a recommended control strategy.)
The following settings are used for the Tower Fan Staging Only
mode, (SP = setpoint)
A. TOWER Setpoint Screen
1. SP1. Select TEMP if control is based on condenser
EWT or LIFT if based on compressor lift expressed in
pressure.
2. SP2. Select NONE for no bypass valve or fan VFD
control.
3. SP3. Select one to four fan outputs depending on the
number of fan stages to be used. More than one fan
can be used per stage through the use of relays.
4. SP4. Select STAGE UP TIME from 1 to 60 minutes.
The default value of 2 minutes is probably a good
starting point. The value may need to be adjusted later
depending on actual system operation.
5. SP5. Select STAGE DOWN TIME from 1 to 60
minutes. The default value of 5 minutes is probably
a good starting point. The value may need to be
adjusted later depending on actual system operation.
6. If TEMP is selected in SP1, use
a. SP6. Select STAGE DIFFERENTIAL in degrees F.
Start with default of 3°F.
b. SP8-11. Set the STAGE ON temperatures
consistent with the temperature range over which
the condenser EWT is desired to operate. The
default values of 70°F, 75°F, 80°F and 85°F are a
good place to start in climates with moderate wet
bulb temperatures. The number of STAGE ON
setpoints used must be the same as SP3.
7. If LIFT is selected in SP1, use
a. SP7. Select STAGE DIFFERENTIAL in PSI. Start
with default of 6.0 PSI.
b. SP12-15. Start with default setpoints. The number
of STAGE ON setpoints used must be the same as
SP3.
(II) VALVE SP: Tower Fan Staging With Bypass Valve
Controlling Minimum EWT
A. TOWER Setpoint Screen
1. Use all of the same setpoint settings as those outlined
in section I.A [the TOWER Setpoint Screen section for
control strategy (I) NONE] except for SP2. For SP2,
select VALVE SP for control of the bypass valve based
on temperature or lift.
B. VALVE Setpoint Screen
1. SP1. Select NC or NO depending if valve is
normally
closed
to the tower with no control power or
normally
open
to the tower with no control power.
2. If TEMP was selected for SP1 on the TOWER
Condenser
MicroTech
®
II
Controller
Bypass Line
0-10 VDC Signal
BAS
Tower
Control
Panel
w/ Fan
VFD